1. Field of the Invention
The invention relates to a microswitch having a magnetic field or gauss sensor, a switch device varying its switching status in accordance with magnetic induction at the magnetic field sensor, and two permanent magnets generating magnetic fields having a boundary region in which the magnetic field sensor is disposed.
U.S. Pat. No. 3,226,631 already discloses a magnetic field switch in which two permanent magnets that are disposed with their axes parallel, are each joined by one pole of the same name or polarity through a yoke, while the other poles that are also of the same name or polarity as each other each have a pole piece, and free ends of the pole pieces form a gap in which a magnetic field sensor is disposed. If a ferromagnetic tripping body, such as an iron rail, is moved across the gap, that is detected and evaluated through the magnetic field sensor. However, the layout for a microswitch as shown therein is overly complicated and too large.
2. Summary of the Invention
It is accordingly an object of the invention to provide a microswitch with a magnetic field sensor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which is constructed simply, with as few and as small components as possible, and which enables reliable actuation without being vulnerable to undesirable extraneous influences.
With the foregoing and other objects in view there is provided, in accordance with the invention, a microswitch, comprising two coaxial columnar permanent magnets having poles of the same name or polarity facing one another defining an air gap therebetween, the permanent magnets generating magnetic fields defining a boundary region; a magnetic field sensor being disposed in the boundary region and fixedly disposed in the air gap; and a switch device being connected to the magnetic field sensor and having a switching status varying in accordance with magnetic induction at the magnetic field sensor.
With the objects of the invention in view, there is also provided a microswitch, comprising two coaxial columnar permanent magnets having poles of different names or polarities facing one another defining an air gap therebetween, the permanent magnets generating magnetic fields defining a boundary region; a chip-like magnetic field sensor being disposed in the boundary region and fixedly disposed in the axial direction in the air gap; and a switch device being connected to the magnetic field sensor and having a switching status varying in accordance with magnetic induction at the magnetic field sensor.
Accordingly, in the switch of the invention the two permanent magnets are disposed directly one above the other, in such a way that they themselves form the air gap for the magnetic field sensor, making additional yokes or pole pieces unnecessary. Small, for instance round magnets may be used for the configuration, so that overall a switch of very small volume can be made.
In accordance with another feature of the invention, the two permanent magnets are disposed at a fixed distance from one another, and the magnetic field sensor in the air gap is likewise fixed in a fixed relationship with the two permanent magnets, in such a manner that the magnetic induction at the magnetic field sensor in the position of repose is adjusted to a fixed value, and upon approach of a ferromagnetic tripping body to a pole of one of the permanent magnets remote from the magnetic field sensor, or to one of the sides of one of the permanent magnets that are parallel to the axial direction, the magnetic inductance assumes a magnitude that is varied as compared with the position of repose and can be evaluated by the switch device.
The configuration of the magnetic field sensor is thus separate from the switching range for the tripping body at one of the outer permanent magnet poles. Once again, this permits an especially simple layout of the switch.
In accordance with a further feature of the invention, a first one of the two permanent magnets is fixed in a fixed association together with the magnetic field sensor, a second one of the two permanent magnets is guided displaceably in the axial direction and is biased by a restoring force into a position of repose remote from the magnetic field sensor, in the position of repose a magnetic induction that is effective at the magnetic field sensor can be evaluated, and upon displacement of the second permanent magnet counter to the restoring force into a working position, the measured induction at the magnetic field sensor is decreased by an evaluatable amount.
In accordance with an added feature of the invention, the magnetic repulsion between the two permanent magnets is used as the restoring force. This provides an especially simple construction.
In accordance with an additional feature of the invention, the second permanent magnet is connected to an actuation tappet of non-ferromagnetic material that is axially guided in a housing.
In accordance with yet another feature of the invention, the magnetic field sensor is a Hall sensor or a magnetoresistor (field plate), depending on the conditions of use. Other magnetic field-sensitive elements, such as magnetic field diodes and the like, are also conceivable.
In accordance with a concomitant feature of the invention, there are provided terminals of the switch being constructed as insulation displacement connection terminals.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a microswitch with a magnetic field sensor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing.